1. Field of the Invention
The present invention relates to a shaft coupling device used for a movable object which rotates about a shaft, more particularly, to a shaft coupling device used for a mechanically shaft coupling device, a mechanically coupling clutch device or a mechanically coupling brake device for a shaft.
2. Description of the Related Art
U.S. Pat. No. 2,783,861 (Robert N. Jungles et al.) published on Mar. 5, 1957 disclosed a driven-released brake. In the technical scheme disclosed in the above publication, a movable member and a static member are constantly kept in a friction engagement state in which the movable member engages with the static member during force transmission process. Therefore, the driven-released brake of the above invention is problematic in that the brake is likely to be heated during transmission. As a result, power consumption of the brake is increased.
U.S. Pat. No. 2,838,150 (Clarance M. Eason et al.) published on Jun. 10, 1958 disclosed a compressed air operated clutch and mechanically connected brake. In the technical scheme disclosed in the above publication, a movable member and a static member are kept in an engagement state in which the movable member engages with the static member during transmission process when the clutch is driven to be in an engagement state by compressed air. When the clutch is kept in a released state, force generated by a driving member is necessitated so as to achieve a braking function.
U.S. Pat. No. 3,994,376 (David A. Fuighum et al.) published on Nov. 30, 1976 disclosed a self-actuating mechanism for braking a driven member upon discontinuating of drive thereto. In the technical scheme disclosed in the above publication, force is required to be applied to a driven member from a driving member when rotational movement is needed to be stopped.
PCT Publication WO96/01380 (application No. PCT/CN95/00055) published on Jan. 18, 1996 discloses a constant closed brake. The brake is provided with a brake spring which is provided on a brake disk and a coupling disk. A connection member associated with an external force association member is provided on a member which is associated with an engageable concave-convex surface associated with a convex/concave surface of the brake disk. The concave-convex surface is separated from the brake disk, and the brake disk is associated with the external force association member through engagement between the brake disk and the concave-convex surface. Therefore, the brake disclosed in this application is complicatedly constructed. The position of the compensation block of the friction gap adjustment and compensation device is not confined along the circumference direction. When the force applied by the external connection member is greater than the braking spring force, the brake disk disconnects from the friction block. On the other hand, the brake disk engages with the friction block as long as the force applied by the external connection member is less than the braking spring force. No device is provided to ensure the coupling device to be in a disconnected state when the brake disk disconnects from the friction block. Further, the coupling device is not provided with an overload protection device during transmission. Moreover, the gap adjustment and compensation device is not sufficiently limited to its position. In other types of constant closed brake, such as an electromagnetic brake, an electromagnet used as a force generating source is kept in a turn-on state during which the brake disk disconnects from the friction block.